Characterisation of the bacteriostatic and bactericidal mode of action of antibacterial proteins and compounds using Laser Scanning Confocal Microscopy

Abstract

Antibiotic resistance is an expanding global health concern requiring new and innovative approaches to prevent and treat bacterial infections. Bacteriophages and their products are one possible solution to combat these drug-resistant pathogens. The genomes of various bacteriophages have been mined for novel activities and are a rich source of proteins that have evolved to disrupt bacteria. A diverse family of such proteins, known as Kil proteins, are encoded by several Escherichia coli bacteriophages and appear to target the cell division apparatus, notably FtsZ which is essential for bacterial cell division. In this thesis I demonstrate that a group of structurally dissimilar Kil proteins when expressed in E. coli induce cell filamentation and promote cell killing. All these proteins are small in size and could be developed as peptide inhibitors that target FtsZ and other components of cell division. This thesis also examines the effect of metal chelating agents on bacterial growth and viability. Chelators are well known inhibitors of bacterial growth, but their antibacterial mechanism of action is poorly characterised. Here, a number of compounds were probed for their impact on bacterial cell morphology and potential for disrupting membrane integrity, redox chemistry and membrane potential. The results reveal that there is no single mechanism of action shared by these metal chelators but does reveal specific effects that provide fresh insights into different mechanisms of bacterial growth inhibition in addition to metal deprivation. All the proteins and compounds studied show potential as novel antibacterial agents that could be employed to treat bacterial infections.